Beam type electron tube



Oct. 21, 1952 c, GRIMM 2,615,138

BEAM TYPE ELECTRON TUBE Filed 061 30, 1948 Patented st. 21, 1952 UNH'E2,ti5,l38

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BEAIW TYPE ELECTRON TUBE Albert C. Grimm, Lancaster, Pa., assignor toRadio Corporation of America, a corporation of Delaware ApplicationOctober 30, 1948, Serial No. 57,593

11 Claims. 1

This invention relates to electron tubes, and particularly to electrontubes of the type used as deflection tubes in the deflection circuits ofcathode ray tubes as employed, for example, in television systems, radarsystems and the like. However, the invention may be used in any circuitwherein a tube works into a reactive load.

The deflection circuits of cathode ray tubes used in television andsimilar systems comprise an electron tube upon whose control grid isimpressed a succession of pulses. The, resulting pulses of anode currenttraverse the primary of a transformer whose secondary supplies thedeflection coil or plates of the cathode ray tube. In such deflectingcircuits, the sudden interruptions of current in the transformer anddeflecting yoke windings set up undesirable oscillations in thesecomponents due to shock excitation, necessitating some form ofunidirectional damping to suppress these oscillations. Conventionallythis damping is accomplished by an electron tube connected in parallelwith the secondary of the transformer. In deflection circuits so damped,inadequate damping of the primary circuit of the transformer, due toimperfect coupling between the primary and secondary circuits of thetransformer, allows the primary circuit to oscillate during the re-tracetime and that portion of the scansion period when the deflection circuittube is cut off. The oscillations may be of such magnitude that on theirnegative peaks the anode potential of the deflection tube fallssufliciently far below the potential of the screen grid of the tube thatthe proper relations exist for generation of electronic oscillationswithin the tube, presumably cf the Barkhausen-Kurtz type. The

oscillations are undesirably produced within the conventional deflectiontube and by the associated circuit cause very objectionable interferenceevidenced in television systems by severe impairment of the quality ofthe received picture.

Various arrangements and methods have herefore been proposed to suppressor reduce such undesired oscillations, but in general they have requiredadditional circuit components including expensive transformers whosewindings must have low capacity to ground and be insulatedfrom eachother to withstand differences of potential of the order of severalthousand volts.

In accordance with the present invention, such external circuitcomponents, with their attendant cost and problems, are unnecessary andthe damping of the undesired oscillations is effected within thedeflection circuit tube itself.

In accordance with the present invention, such undesired oscillationsare prevented by providing within the deflection circuit tube itself adamping path or circuit avoiding need for external circuit componentssuch as high-voltage diodes and transformers with the attendant problemsof low capacity and high-voltage insulation as well as additional cost.More specifically, in addition to its usual electrodes, the tube of thepresent invention is provided with an auxiliary cathode heated toemission temperature by bombardment of electrons moving toward the anodeof the tube. The electrons emitted by this auxiliary cathode arecollected by an auxiliary anode within the tube, or, in the case of abeam tetrode, by the beam-focusing electrode which also serves as theauxiliary anode. The auxiliary cathode and anode are connected to themain anode and cathode, respectively, of the tube so to provide aunidirectional damping path eifective to suppress the undesiredoscillations.

This invention corrects two important types of interference, namely,high frequency electronic oscillations generated within the tube and lowfrequency oscillations generated by oscillation of the transformerwindings. Complete suppression of the low frequency oscillation removesthe negative potential from the tube anode and thus prevents highfrequency oscillations within the tube.

The object of this invention is to provide an improved electron tubestructure.

More specifically the principal object of the invention is to providemeans within an electron tube for effectively suppressing oscillationswhich could'otherwise be produced'in the tube due to oscillationsoriginating in the external anode circuit thereof.

Another object of the invention is to provide an electron tube having aselements at least an anode and a cathode with means for producing anauxiliary unidirectional conducting path within the tube in shunt withthese elements.

A further object is .to provide an electron tube having electrodesdetermining a main electron path with auxiliary cathode structuredisposed in this path for heating by electron bombardment and auxiliaryanode structure to collect electrons emitted by auxiliary cathodestructure.

The invention further resides in features of construction, combinationand arrangement hereinafter described and claimed.

For a more detailed understanding of the invention, reference is made tothe accompanying drawings in which:

, Fig. l is a plan view of the electrode arrange- 'ment of a tubeembodying my invention;

Fig. 2 is a schematic diagram of a cathode ray 3 tube deflection circuitin which my improved tube may be used;

Figs. 3 and 4 are explanatory figures referred to in the explanation ofthe operation of my improved tube;

Figs. and 6 are perspective views of the electrode arrangements of twobeam tetrodes embodying my invention; and

Fig. '7 is a plan view of a modification of the structure shown in Fig.5.

Referring to Fig. l, the tube comprises a cathode I, control grid 3,screen grid 4 and anode 5. Each of these electrodes has. substantiallength normal to the plane of Fig. l. The cathode I may be of thedirectly heated type, or, as shown, there may be provided an internalheater 2 for raising the temperature of the cathode to electron-emissivetemperature. The cathode, grids and grid supports are so constructed andarranged that during operation of the tube the stream of electrons,generally indicated by the dotted lines, passing through the mesh of thecontrol grid 3 and the screen grid 4 in its movement to the anode 5v isfocused into a divergent beam, as shown in dotted lines. It will beunderstood that the electrode structure will be enclosed and mountedwithin an evacuable envelope (see Fig. 2). The tube construction as thusfar described is conventional and tubes so constructed are productive ofundesired oscillations when used in cathode ray tube deflectioncircuits, and analogous applications wherein the tube works into aninductive load, for reasons above discussed.

In accordance with my inventiornin order to suppress such oscillations,the tube is provided with one or more auxiliary cathodes 6 disposed inthe path of electrons moving from the main cathode I to the anode 5.These auxiliary cathodes, which may be in theform of filaments, arepreferably disposed in the region adjacent the plate or anode 5 and aredirectly electrically connected thereto as by the supporting bars orwires 1. Each of the auxiliary cathodes 6, shown in end view in Fig. 1,is of substantial lengthas measured transversely of the electron streamand is rigidly supported as by one or more supports 7. One of thesupports may be spring loaded to tension the filament.

Because of their location, the auxiliary cathodes .6 are bombarded byelectrons moving toward the anode 5 and are heated by such bombardmentto electron-emissive temperature so that each becomes a source ofelectrons distinct from the main cathode i.

In the particular form of tube shown in Fig. 1, the electrons emitted bythe auxiliary cathodes 6 are collected by one or more auxiliary anodes 8which are disposed outside of the path of electrons moving from the maincathode I to the main anode 5. The-auxiliary anodes 8 may be connectedto the main cathode l within the tube itself, or may be connected toseparate terminal structure for external connection to portions of thecircuit at other than cathode potential. Each of the cathodes t with itsassociated auxiliary anode 8 for-msa diode providing a unidirectionaldamping path in shunt with the main-anode 5 and cathode l within thetube itself. As the auxiliary cathode 6 is heated by electronbombardment, there does not arise the problem of providing insulationbetween a heating circuit for the auxiliary cathode and the high voltageapplied to the anode 5.

Referring toFig. 2, the tube ill, generically representative of thetubes shown in Figs. -1, 5, 6,

and 7, is included in a deflection circuit or system for supplyingsawtooth current impulses to the deflection coil ll of a cathode raytube l2. Appropriately shaped voltage impulses produced by a pulsegenerator l3 are impressed upon the control grid 3 of tube Hi. In theanode circuit of the tube I0 is included the primary winding I4 of acoupling transformer whose secondary winding 15 is connected to thedeflection coil H. A diode I6 is provided for damping oscillations inthe secondary winding l5. As appears from Fig. 2 and from the foregoingdescription of Fig. l, the auxiliary cathodes 6 and auxiliary anodes 8form within the tube envelope a unidirectional conductive path or pathsin shunt to the primary winding I 4 of the coupling transformer Thepath'or paths so provided within the tube 10 damp out oscillationsotherwise produced when the primary circuit is unloaded during part ofeach scanning pulse applied to the control grid 3.

Fig. 3 illustrates the plate voltage wave form of a conventional tubeused in a deflection circuit similar to that shown in Fig. 2. The loops2!) represent the undamped oscillations in the plate voltage caused byoscillations in the primary winding I4 of the coupling transformer.

Fig. 4 illustrates the plate voltage wave form of my improved tube inthe circuit .of Fig. 2. The diode incorporated in the deflection tube l0quickly clamps out the oscillations, as shown by the loops- 2 I.

When, as shown in Fig. 5 the tube is of the beam tetrode type usingbeam-forming or beamfocusing electrodes 8d at cathode potential, theseelectrodes, in addition to their normal beamfocusing function, may alsoserve as the auxiliary anodes for collection of electrons emitted by thebombarded auxiliary cathodes 6. The auxiliary cathodes 6 may be ofribbon form supported at each end by plates 1, as shown. In otherrespects the electrode arrangement shown in Fig. 5 is similar to that ofFig. '1 and accordingly further description thereof is unnecessary. Inboth figures, corresponding elements have been identified by likereference characters. In brief, in Fig. 5 the auxiliary cathodestructure 6 is disposed within themain beam of electrons and connectedto the main anode 5, and the electrons emitted by the auxiliary cathodestructure .6 are collected by auxiliary .anode structure formed by theedges of .thebeam forming electrodes 8a which are outside of the mainbeam of electrons and connected to the main cathode l.

The tube shown in Fig. 6 is similar to that of d Fig. 5 with theexception that only one auxiliary cathode 6a is provided in the beampath. on each side of the elliptical cathode and grid structure.However, eachauxiliar cathode 6a and the two adjacent edges of thetwobeam forming electrodes 8a form two damping diodes in shunt with themain anode and maincathode.

' Fig. 7 showsamodification of the tube of Fig. 5 wherein-the edges ofthe beam forming electrodes llaare provided with fiangesor similarprojections 8b to serve as the auxiliary anodes of'the shunt diodes.

It is not necessary that the auxiliary. anodes be located outside thebeam path, as illustrated and. described in the specific examples given,.although that is the preferred arrangement. If the auxiliary anodeswere in the beam path, the

beam would Lbeslightly deflected, but otherwise the tube-would functionnormally.

It will be understood. that the invention is not limited to theparticular tubes described and .il-

3 lustrated, and that changes and modifications may be made within thescope of the appended claims.

What is claimed is:

1. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said main cathode tosaid main anode, auxiliary cathode structure disposed within said pathfor heating by electron bombardment, and auxiliary anode structuredisposed outside of said path to collect electrons emitted by saidauxiliary cathode.

2. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said main cathode tosaid main anode, auxiliary cathode structure disposed within said pathfor heating by electron bombardment and directly connected internally ofthe tube to said main anode, and auxiliary anode structure disposedoutside of said path for collection of electrons emitted by saidauxiliary cathode.

3. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said main cathode tosaid main anode, auxiliary cathode structure disposed within said pathfor heating by electron bombardment, auxiliary anode structure disposedoutside of said path for collection of electrons emitted by saidauxiliary cathode, and connections within the tube connecting saidauxiliary anode and cathode to said main cathode and anode,respectively.

4. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said main cathode tosaid main anode, auxiliary cathode structure disposed adjacent saidanode and in said path for heating by electron bombardment, andauxiliary anode structure disposed outside of said path for collectionof electrons emitted by said auxiliary cathode.

5. An electron tube comprising a cathode, control and screen grids andan anode determining an electron path for electrons from said cathode tosaid anode, and means within said tube for preventing the anodepotential from falling to substantial negative values relative to saidcathode during operation of said tube comprising auxiliary cathodestructure disposed in said electron path for heating by electrons movingtoward said anode, and auxiliary anode structure disposed outside ofsaid path for collection of electrons emitted by said auxiliary cathode.

6. A beam tube comprising a cathode, a grid,

, beam-focusing electrode structure and an anode determining a beam pathfor electrons from said cathode to said anode, and means within saidtube for suppressing conditions which bring about oscillationscomprising auxiliary cathode structure disposed within said beam pathand adjacent said beam-focusing electrode structure for heating byelectron bombardment, said beam-focusing electrode structureadditionally serving as auxiliary anode structure for collection ofelectrons emitted by said auxiliary cathode.

7. A beam tube comprising a cathode, a grid, beam-focusing electrodestructure and an anode determining a beam path for electrons from saidcathode to said anode, and means within said tube for suppressingconditions which bring about oscillations comprising auxiliary cathodestructure disposed within said beam path and adjacent said beam-focusingelectrode structure for heating by electron bombardment, saidbeam-focusing electrode structure additionally serving as auxiliaryanode structure for collection of electrons emitted by said auxiliarycathode, said auxiliary cathode structure being mounted on andelectrically connected to said anode, and said beam-focusing electrodestructure being electrically connected to said cathode.

8. An electron tube comprising a cathode, an anode spaced from saidcathode in position to receive electrons therefrom, and means forpreventing the anode potential from falling to substantial negativevalues relative to said cathode during operation of said tube comprisingauxiliary cathode structure disposed in the path of electrons from saidcathode to said anode for heating by electron bombardment and auxiliaryanode structure spaced from said auxiliary cathode structure in positionto collect electrons emitted thereby, said auxiliary anode structurebeing directly connected to said cathode.

9. An electron tube comprising a cathode, an anode spaced from saidcathode in position to receive electrons therefrom, and means forpreventing the anode potential from falling to substantial negativevalues relative to said cathode during operation of said tube comprisingauxiliary cathode structure disposed in the path of electrons from saidcathode tosaid anode for heating by electron bombardment and means forcollecting electrons emitted by said auxiliary cathode structure.

10. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said cathode to saidmain anode, auxiliary cathode structure disposed within said path forheating by electron bombardment and directly connected to said mainanode, and auxiliary anode structure spaced from said auxiliary cathodestructure in position to collect electrons emitted thereby.

11. An electron tube comprising a main anode, a main cathode spaced fromsaid main anode to define a path for electrons from said main cathode tosaid main anode, auxiliary cathode structure disposed Within said pathfor heating by electron bombardment, auxiliary anode structure spacedfrom said auxiliary cathode structure in position to collect electronsemitted thereby, and connections within the tube connecting saidauxiliary anode and cathode to said main cathode and anode,respectively.

ALBERT C. GRIMIW.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,134,407 Jonker 1 Oct. 25, 19382,273,546 Van Weel Feb. 1'7, 1942 2,293,418 Wagner Aug. 18, 1942

